If the existing law against felons owning guns was enforced,
this would not be a problem. However, if the existing gun and drug laws were enforced,
no-one would be calling for gun registration.
Convicted felons such as Buford Furrow and H. Rap Brown know that the law is not enforced.
Convicted knife-attacker Buford Furrow was allowed to keep his guns after his conviction,
despite the Federal law to the contrary.
He used those guns to shoot children at a Jewish Day Care Center and kill a mailman.
Nobody bothered to enforce the law.
Convicted robber H. Rap Brown was allowed to illegally buy an assault weapon.
He used it to kill a policeman. Nobody bothered to enforce the law.

The Fifth Amendment also protects other criminals from gun registration.
Every criminal can protect his guns by committing a felony crime and getting probation,
or by giving his guns to a convicted felon for safekeeping.

Fatal Flaw #2: Guns can be hidden in drug shipments

According to US Federal Government agencies,
drug smugglers slipped 690,000 pounds of cocaine past police in the first 6 months of 2000.You can hide thousands of guns in 690,000 pounds of cocaine!
Of course drug smugglers also bring in hundreds of thousand of pounds of marijuana,
heroin, and other illegal drugs besides cocaine.
Guns are readily available from China, Russia, Eastern Europe, and major drug-producing countries.
The Chinese Army is the world's largest manufacturer of assault rifles,
and they sell them to anyone, even terrorists.
Will drug dealers register their illegal smuggled guns?

What are you going to do,
X-ray every drug shipment to make sure that there aren't any guns hidden in the cocaine?